One common way to perform surface inspections of subsea structures such as pipelines, pilings, risers, and boat hulls is to navigate a remotely operated vehicle (ROV), such as by utilizing thruster jets, to the inspection surface, and to then deploy one or more robotic arms having inspecting tools therein. ROV-based inspections are particularly suitable for subsea pipelines that are vertically or horizontally installed in the ground, or suspended from a support structure.
It can be a challenge to maintain ROV stability during inspection, especially if the inspection surface is a structure suspended in water because such structures are less stable than seabed-implanted structures. Specifically, the challenge arises from reaction forces generated upon contact of inspection tools to the surface being inspected or cleaned. Since the ROV floats underwater, the ROV is particularly sensitive to such reaction forces due to buoyancy effects and the reaction forces can easily push the ROV backward to destabilize it. In particular, deploying cleaning jets, rotating brushes, and other marine life cleaning tools at an inspection surface imparts strong reaction forces to the ROV robotic arm, which leads to frequent destabilizations. Re-stabilizing the ROV or counteracting the reaction force can be accomplished by activating thrusters to provide a continuous thrust force in opposition to the reaction force. However, increased thruster use has several drawbacks. For instance, activating the thrusters depletes ROV battery power, thereby reducing ROV uptime. Constant re-stabilizing also agitates the seabed and churns the water, which reduces operator visibility, and introduces costly delays from continually having to reorient the robotic arm to the inspection surface.
As such, there exists a need for mechanical solutions to improve stabilization of ROVs during inspection and cleaning tasks without utilizing thrusters, in particular when such tasks are performed on pipelines. It is in regard to these issues that the present application is provided.